In a semiconductor device manufacturing process, as an apparatus for processing a substrate such as, for example, a semiconductor wafer (hereinafter, referred to as a “wafer”), there is a plasma etching apparatus in which etching is performed on the wafer by irradiating the wafer with plasma.
In plasma etching, a gas containing, for example, fluorine, chlorine, or oxygen is used as a processing gas to generate plasma. The plasma includes active species such as, for example, charged particles (hereinafter, referred to as “ions”) and neutral particles (hereinafter, referred to as “radicals”). The surface of the wafer reacts with the plasma including ions and radicals to produce reaction products, and the produced reaction products are volatilized, so that etching is performed.
In the semiconductor device manufacturing process, wafers have recently been enlarged in diameter. With the enlargement in diameter of wafers, it is difficult to secure in-plane uniformity of a line width (critical dimension (CD)) and a depth of a hole or a bottom of a trench in a wafer plane during etching.
Meanwhile, there is also a technique for controlling a density distribution of radicals in a central region and a peripheral region in a wafer plane by adjusting an amount of a processing gas supplied from an upper electrode.